This proposal is focused on the transfer of mitochondria during cell division, using the yeast S. cerevisiae as the model system. From previous studies, the PI hypothesized that 1) Arp2/3 complex-mediated actin nucleation on the mitochondrial surface generates the forces for mitochondrial movement; 2) a mitochondrial actin binding protein (mABP) mediates the association with actin cables; 3) polarized actin cables serve as tracks to guide motile organelles from mother cell to bud. During the next funding period, Dr. Pon proposed to test the role of candidate mABP proteins in mediating interactions between mitochondria and actin in vivo and vitro. She will study a putative mitochondrial receptor complex for binding Arp2/3, including its subunit composition and its potential regulatory effects on Arp2/3 and mABP. Dr. Pon will also visualize mitochondrial interactions with actin cables in living cells, and study the effects of mutations that perturb the Arp2/3 complex and actin cable polarity. Finally, Dr. Pon will test her model for actin based mitochondrial motility, by reconstituting the movement using purified organelles and proteins.